Conventionally, a lighting device is used to cause light, which is emitted from a light emitting diode (LED), to reflect or refract using a reflecting mirror (reflector) or a lens, in order to irradiate a target surface with the light from the LED.
Such lighting device suffers from a fact that illuminance unevenness (often referred to as illumination irregularity or irradiation unevenness) occurs on a surface (plane) irradiated with the light. Various countermeasures are studied to suppress the illuminance unevenness.
For example, Japanese Patent Application Laid-Open Publication No. 2015-164098 (Patent Literature Document 1) discloses an arrangement that includes a light diffusing part disposed on or near the light exit surface of a lens, and another light diffusing part on a surface of a recess formed in the light exit surface, such that the light emitted from the LED uniformly diffuses, and the illuminance unevenness (illumination irregularity, or irradiation unevenness) on the surface irradiated with the light decreases.
In the field of general illumination, on the other hand, a person would be dazzled if the light having high luminance is present in the viewing angle of the person (such phenomenon is called glare). An environment, which frequently has glares, gives uncomfortableness to the person. Thus, countermeasures to suppress the generation of the glare are studied.
For example, Japanese Patent Application Laid-Open Publication No. 2010-102913 (Patent Literature Document 2) discloses an arrangement for a downlight lighting device, and a guide body (mechanism to block or shield the light in a wide angle) configured to suppress the glare is attached to the lighting device. This shields the emitted wide-angle light, which would otherwise enter the viewing angle of the person, and prevents the generation of the glare. A guide body that adjusts the shielding angle may be a shielding device having a pinhole shape (hereinafter referred to as a “pinhole device”), with an opening diameter being decreased.